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Why there is an internal resistance in the batteries?

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Clarkdale44

Member
Hello

My question might seem very obvious but i never really understood why... Too much power is being wasted during charging because of this internal resistance, there must be a logical explanation for this and i need that to know.

I am not looking for technical answer instead if you could explain it to me in simple and short manner then i would really appreciate it...

Regards!!
 

ChrisP58

Well-Known Member
Well, the simple answer is that everything (other than a few materials classed as superconductors at very low temperatures) have some resistance. Even copper (or silver) wire.

But in the case of batteries, there are other factors that impede the flow of current in and out, besides the resistance of the material.

Batteries are made of cells that are electrochemical devices. They store electrical power when the charge current flowing into the cell cause a chemical change to occur. That chemical change is reversed when the cell is discharged. Some of what appears as internal resistance, is actually the inefficiency of those electrochemical reactions when they produce heat as a byproduct of the process.
 

spec

Well-Known Member
Most Helpful Member
Different battery types have different charging efficiencies, which is the difference between the input energy and and the output energy. Under perfect conditions, of temperature, charge current and discharge current, lead acid batteries have a charging efficiency of 85% while under the same ideal conditions a Lithium Ion (LiIon) battery can have an efficiency of 99%. As ChrisP58 says, the lost energy heats the battery.

spec
 
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Rich D.

Active Member
Your question sounds like it might be worded to ask "why do 'they' put an internal resistance in a battery?" Nobody adds an internal resistor in there. It is inherent in the battery chemistry as described above. It is helpful for calculating currents etc. to think of it as a discrete resistor. Smaller, weaker batteries tend to have more resistance. A big-ass powerful battery has very low resistance.
 

Ratchit

Well-Known Member
Hello

My question might seem very obvious but i never really understood why... Too much power is being wasted during charging because of this internal resistance, there must be a logical explanation for this and i need that to know.

I am not looking for technical answer instead if you could explain it to me in simple and short manner then i would really appreciate it...

Regards!!
Internal resistance is caused by the resistance encountered by the charge carriers within the battery. It is the same when charge carrier electrons move in a wire. It is energy that is wasted, not power. Power is the energy rate, and you cannot "waste" a rate. Neither can you store power. Who is to say how much energy waste is too much?

The following comments pertain to others that have answered your post. You don't charge or discharge a battery. Batteries contain the same amount of charge at all times. When a battery is first manufactured and shipped from the factory, it is fully energized. After it is used, it is deenergized. A battery is an electron pump, not a charge storage device. Just as a pump does not store water, neither does a battery store electrons. Batteries store energy. Electrons do not flow through a battery. If they did, the battery would short. Electrons from the chemical reaction flow out of one terminal and into the opposite terminal to be used in another chemical reaction. Naturally, an external conduction path has to be available.

Another descriptive I always run across is the technical slang term "current flow". It means "charge flow flow". One does ot have to say that charge flows twice. Instead, it should be said that current exists or current is present. It is also correct to say charge flows or electrons flow.

Ratch
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
We also talk about ideal voltage and current sources. They dont exist in real life. The ideal voltage source has zero resistance. A lot of times it's called ESR or effective series resistance. CCA (Cold Cranking Amps) is another way to describe ESR but not in resistance units. Some like dealing with big numbers. e.g. 7000 mAh vs 7 mAh. Doesn't 7000 "sound" better?
 

Ratchit

Well-Known Member
We also talk about ideal voltage and current sources. They dont exist in real life. The ideal voltage source has zero resistance. A lot of times it's called ESR or effective series resistance.
Since when has the ESR of a capacitor been taken to mean the resistance of a voltage source?

CCA (Cold Cranking Amps) is another way to describe ESR but not in resistance units.
Since when has the lower electrochemical action of a battery at below normal termperatures been described as ESR?

Some like dealing with big numbers. e.g. 7000 mAh vs 7 mAh. Doesn't 7000 "sound" better?
Maybe, but what is the point of of that statement in relation to the theme of this thread, which is the internal resistance of a battery.

Ratch
 

Grossel

Well-Known Member
<not so great answer>
My stupid question back (pretending not reading the earlier ansvers) - Why do human have massive heavy legs, it take so much effort to move them and the weight make us run much slower than animals.
</not so great answer>

But I will say that a battery that could delivery near infinitive current for a short period of time would be a dangerous part to use. Just imagine the damage potential in case of a short circuit. What about an internal failure in the battery?

Personally I wouldn't have stored any AA battery at home if there was a danger potential.
 

Ratchit

Well-Known Member
<not so great answer>
My stupid question back (pretending not reading the earlier ansvers) - Why do human have massive heavy legs, it take so much effort to move them and the weight make us run much slower than animals.
</not so great answer>
Look at the animals in this link that have heavier, more massive legs than a human, and see how fast they can run. http://www.speedofanimals.com/animals/elephant . What about a horse?

But I will say that a battery that could delivery near infinitive current for a short period of time would be a dangerous part to use. Just imagine the damage potential in case of a short circuit. What about an internal failure in the battery?
No different than a high capacitance capacitor energized to a high voltage. If you need a component like that, you have to live with the consequences of failure.

Personally I wouldn't have stored any AA battery at home if there was a danger potential.
Who would? Does that mean that you will not use any device like a flashlight that uses AA batteries in your home?

What has the speed of animals and humans got to do with battery characteristics?

Ratch
 
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